(1) Field of the Invention
This invention relates to medical diagnostic devices and methods and in particular to the electromyographical diagnosis of nerve damage.
(2) Description of the Related Art
Electromyography, as used clinically to diagnose nerve and muscle disorders, involves recording electrical signals (the electromyogram or EMG) from muscles by means of needle electrodes. These signals may be interpreted as normal or as abnormal for each muscle. The abnormal muscles are also graded for their level of abnormality. Usually, many muscles are sampled in order to make a comprehensive diagnosis. The EMG abnormalities may indicate muscle specific disease and nerve specific disease. In the latter, it may indicate a general (diffuse) disorder and focal or multi-focal disorders. The proposed method, henceforth called the EMGAssistant is dedicated to the latter two.
The interpretation of an EMG study as it pertains to the localization of root/plexus/nerve/branch-damagexe2x80x94or, in generality, nerve-segment damagexe2x80x94is an important part of the neurophysiological evaluation of patients. The current practice is based on established nerve-to-muscle wiring tables* and the slow, thinking-it-through, mental reasoning-process on the part of the physician (electromyographer or EMGer). As such, the current practice is far from perfect. It relies heavily on the individual physician capability to memorize complicated wiring tables, the physician""s deducing capabilities and the time allocated to the task. This is especially true when the nerve damage involves more than one segment of one nerve, and/or when there are extraneous abnormalities on the EMG study that do not relate to the nerve damage at hand. These situations can confuse even the best electromyographer and render his diagnosis worthless. This situation is corrected by the EMGAssistant that makes the diagnostic process completely objective, precise, fast and with the ability of checking all possible answers.
Nerve-to-Muscle Wiring: This program uses the Peripheral Nervous System Nerve-to-Muscle Wiring Tables 1 and 2 to translate combinations of nerve-segment damage to muscle abnormalities and vice versa. These Nerve-to-Muscle Wiring tables are an educated compromise of many sources:
1. Medical Research Council, Memorandum No. 45: Aids to the examination of the peripheral nervous system, Crown, London, 1976.
2. E F Delagi and A O Perotto: Anatomic Guide for the Electromyographer, C C Thomas, Springfield, Ill. 1980.
2. R K Sethi and L L Thompson: The Electromyographer""s handbook, Little, Brown and company, Boston, 1989.
4. J Kimura: Electrodiagnosis in Diseases of Nerve and Muscle, P A Davis, Philadelphia, 1989.
5. J A Liveson: Peripheral Neurology, F A Davis Company, Philadelphia, 1991.
6. R D Adams and M Victor: Principles of Neurology, McGraw-Hill, New York, 1993.
7. A O Perotto: Anatomic Guide for the Electromyographer: The Limbs and Trunk, C C Thomas, Springfield, Ill, 1994.
8. L P Rowland: Merritt""s Textbook of Neurology, Williams and Wilkins, Baltimore, 1995.
9. R J Joynt and R C Griggs: Clinical Neurology, Lippincott Williams and Wilkins, Philadelphia, 1998.
The current practice of nerve-damage localization by EMG is fraught with human drawbacks. The basic idea behind the EMGAssistant program is to implement the human EMGer""s practical and logical endeavors in making EMG diagnosis onto a computer program, that is to find the minimum locations (preferably only one) of nerve-damage that best explain the EMG findings, both the normal and the abnormal ones. At times, the diagnosed nerve-damage location explains the EMG finding completely and at times it does not. In the latter, the EMGer has to make a choice that might not explain some of the EMG findings and may even contradict others (normal and/or abnormal ones). The EMGer uses the severity of the EMG findings and the way they aggregate to guide him to the best diagnosis. The EMGer has to ascertain that any other diagnosis, that is any other nerve-damage location, will explain his findingxe2x80x94normal muscles and the severity of the abnormal onesxe2x80x94even less. The EMGAssistant program follows the mental process the human EMGer goes through. The difference is in that the program will take into consideration all the possible nerve-damage combinationsxe2x80x94literally thousands of them in some casesxe2x80x94while the human EMGer would not, and, in practicality, could not.
Basically, the elecromyographer (EMGer) performs his routine EMG study, assigns graded levels of pathology to each of the muscles he examined. This data is input into the program. A priori, the program computes all the possible combinations (sets) of nerve-segment damage, translates them to all possible combinations (sets) of corresponding muscle damage. Once the data is input, the program compares the input with all these muscle-sets using statistical fit criteria. Once the muscle-sets that best fit the EMGer""s input are found, they are translated to the nerve-sets that theoretically would have produced them. Among the latter, only the nerve-sets that include the minimum number of damaged nerve-segments are retained and output as the best explanation for the EMGer""s findingsxe2x80x94the diagnosis.